Exposure device

ABSTRACT

The present invention relates to an exposure device for living cell cultures, the device having a medium chamber common to a plurality of cell culture chambers and medium directing means. The medium chamber, cell culture chambers and the medium directing means may be arranged so as to provide substantially contemporaneous medium exchange at the cell culture chambers.

The present invention relates to an exposure device for fluid mixtures,in particular cigarette smoke and/or gas mixtures, on living cellcultures.

Various exposure devices are known for the delivery of gaseous matter toliving cell cultures. Each of the known devices facilitates the deliveryof smoke to a cell culture chamber and the delivery of nutrient mediumto the base of cell cultures grown in the cell culture chamber. Theknown devices provide complicated and often costly apparatus designed toprevent mixing of the gaseous matter and the nutrient medium. Forexample, DE 195 26 533 describes an exposure device in which the gaseousmatter is introduced into the top plate of the device and fed by radialsmoke distribution means to distinct and separate cell culture chambers.The gaseous matter is then fed away from above the cell culture chambersto a central air outlet in the base plate of the exposure device. Thegaseous matter is thus fed directly onto the top surface of the cellcultures. The nutrient medium is supplied to each cell culture chamberthrough inlet and outlet channels connected to reservoirs in the baseplate of the device, each cell culture chamber being located in aseparate reservoir, thus keeping the gaseous matter and the nutrientmedium separate as well as providing independent medium supply to eachof the cell culture chambers. The apparatus described is complicated andcostly to manufacture and requires monitoring of the flow rate of thegaseous matter onto the cells in order to ensure the cells are notdamaged by the gas flow rate. Additionally a number of medium inlet andoutlet pipes are required as each medium reservoir has its own inlet andoutlet channel.

In International Patent Application number WO 99/36505 medium is fedthrough an inlet pipe to a number of separate cell culture chambers.Each cell culture chamber has its own discrete medium chamberthereunder. The apparatus is very complicated and costly to manufactureand does not allow continuous medium exchange at each of the cellculture chambers. The nutrient medium must be removed by the same meansthat supply the nutrient medium to the cells, thus medium must beremoved before fresh medium and/or medium containing additives can beapplied to the base of the cell culture.

It is an object of the present invention to provide an exposure devicefor living cells cultures that has a medium chamber common to all of thecell culture chambers, therefore allowing continuous medium exchange ateach of the cell culture chambers.

It is a further object of the present invention to provide an exposuredevice for living cell cultures that is simple and cheap to manufactureand easy to use.

It is an even further object of the present invention to provide anexposure device for living cultures that is operable to provide eitherbasal or submersion feeding conditions for cells in which the mediumsupply can be set at selected inlet and outlet flow rates with nofurther need for human or electronic intervention.

It is a yet further object of the present invention to provide anexposure device for living cell cultures which, in operation, requiresno balancing of the medium inlet flow rate and the medium outlet flowrate in order to maintain medium supply to the cell cultures growntherein.

The present invention provides an exposure device for living cellcultures comprising a base portion, a top portion, fluid inlet means,fluid outlet means, medium inlet means, medium outlet means, a mediumchamber and a plurality of cell culture chambers, wherein the mediumchamber is common to all of the cell culture chambers.

Preferably the medium chamber has medium directing means therewithin.Advantageously the medium directing means is formed from a raised areaof the base portion of the exposure device. Suitably the mediumdirecting means is an island within the medium chamber around which thenutrient medium may flow. The medium directing means is positionedwithin the medium chamber so as to direct the flow of medium under eachof the cell culture chambers. Preferably the medium directing means iscentrally located within the medium chamber, and is even more preferablylocated equidistant to each of the cell culture chambers.

Preferably the exposure device comprises two or more cell culturechambers positioned such that the base of each cell culture chamber islocated within the medium chamber. Advantageously the exposure devicecomprises three cell culture chambers. The exposure device may besuitably adapted to comprise any number of cell culture chambers andcell culture chambers of varying sizes. Cell culture chambers suitablefor use in the exposure device of the present invention will be readilyknown to those skilled in the art.

Preferably the base of each of the cell culture chambers is spaced apartfrom the base of the exposure device by means of a gap to allow themedium to flow freely under each of the cell culture chambers within themedium chamber. Continuous medium exchange at each of the cell culturechambers is facilitated by the free flow of medium under each of thecell culture chambers. Continuous medium exchange is further enhanced bythe positioning of the medium directing means.

Suitably the gap through which medium is free to flow between the baseof each of the cell culture chambers and the base of the exposure deviceis at least 1 mm. Preferably the gap between the base of each of thecell culture chambers and the base of the exposure device is about 2 mmor more. Even more preferably the gap between the base of each of thecell culture chambers and the base of the exposure device is about 4 mm.

Medium is supplied to the medium chamber of the exposure device bymedium inlet means and is removed from the medium chamber of theexposure device by medium outlet means.

Preferably the medium inlet means is located to supply medium to thebase portion of the exposure device whereby medium flows directly intothe medium chamber. Even more preferably the medium inlet means islocated in a side wall or a bottom wall of the base portion of theexposure device.

Suitably the medium inlet means is a pipe or a tube.

Advantageously the medium outlet means is spaced apart from the mediuminlet means and is separated from the medium inlet means by all of thecell culture chambers and/or the medium directing means.

Preferably the medium outlet means is operable to remove medium from thetop surface thereof and suitably extends from the top portion of theexposure device into the medium chamber. The position of the intake endof the medium outlet means relative to the base of the cell culturechambers may be adjusted to allow for either basal or submersion feedingof the cell cultures. Alternatively, the medium outlet means maycomprise two outlet means, the first positioned to allow for basalfeeding of the cell cultures, and the second outlet means beingpositioned to allow for submersion feeding of the cell cultures.

During basal feeding the medium level is maintained such that medium isalways in contact with the base of the cell cultures. In an alternativeexperimental regime the medium level may be maintained such that thecell cultures are always covered by the medium, such a feeding regimebeing known in the art as submersion feeding.

Suitably the medium outlet means is a pipe or a tube. Preferably themedium outlet means is a retractable tube which may be locked into theexposure device such that the intake end of the tube is at a heightabove the base of the device selected by the operator. The height of theintake end of the tube above the base of the exposure device may beequal to the distance of the cell cultures above the base of the devicein order to facilitate basal feeding of the cultures or, alternatively,the height of the intake end of the tube above the base of the devicemay be greater than that of the cell cultures in order to facilitatesubmersion feeding of the cultures.

Locking of the position of the medium outlet tube may be provided bylocking means. The locking means may be a threaded screw arrangementhaving a central bore, the medium outlet tube passing through thecentral bore of the threaded screw. Alternatively frictional lockingmeans operable to adjust the position of the medium outlet tube may beprovides

Preferably the medium outlet means is operably attached to first pumpmeans, the pump means being operable at a controllable first pump rate.Suitably the first pump rate is in the range of about 1 ml/min. andabout 20 ml/min. Preferably the first pump rate is about 10 ml/min.

The medium inlet means is suitably operably attached to second pumpmeans, the second pump means being operable at a controllable secondpump rate. Suitably the second pump rate is in the range of about 1ml/min and about 10 ml/min. Preferably the second pump rate is about 7ml/min.

Advantageously the first pump rate is at least equal to the second pumprate in order that, in operation, the selected medium level ismaintained without the need for further intervention. Preferably thefirst pump rate is greater than the second pump rate. Preferably thefirst pump rate is greater than the second pump rate and the mediumlevel within the medium chamber does not vary by more than about 3 mmduring operation. Preferably the medium level within the medium chamberdoes not vary by more than about 0.5 mm during operation.

The medium outlet means and/or the medium inlet means may runcontinuously or, alternatively, may supply/remove nutrient medium inpulses at flow rates selected by the operator. When the medium inletmeans is to run continuously, the first pump rate of the medium outletmeans is greater than that of the second pump rate of the medium inletmeans, therefore no balancing of the pumps is required to maintain themedium at a level set by the operator.

Preferably the medium chamber together with the medium directing meansand the medium inlet and outlet means facilitates substantiallycontemporaneous medium exchange at each of the cell culture chambers.The medium directing means and the cell culture chambers are locatedwith respect to one another so that contemporaneous medium exchangeoccurs at each of the cell culture chambers.

The exposure device further comprises a fluid exposure chamber common tosaid cell culture chambers and fluid dispersing means operable toprovide substantially contemporaneous fluid exposure to each of the cellculture chambers.

Preferably the fluid inlet means of the present invention is located inthe top portion of the exposure device. Even more preferably the fluidinlet means is located in the centre of the top portion of the exposuredevice.

The fluid inlet means may be adapted to connect with fluid generatingmeans whereby fluid is delivered to the exposure device through thefluid inlet means.

The fluid is passed through the fluid inlet means to the fluid exposurechamber via the fluid dispersing means. Suitably the fluid dispersingmeans may be a disc-shaped plate above the cell culture chambersoperable to disperse the fluid before the fluid reaches the fluidexposure chamber.

Advantageously the fluid flow rate supplied to the cell culture chambersis up to about 700% of available air space per minute.

Preferably the fluid outlet means is located above the level of themedium within the medium chamber such that medium does not flow throughthe fluid outlet means. More preferably the fluid outlet means ispositioned such that the medium outlet means is at a level lower in themedium chamber than the fluid outlet means.

Advantageously the fluid outlet means may be located in a side wall ofthe base portion of the exposure device or, alternatively, is located ina side wall of the top portion of the exposure device.

Preferably the fluid may be smoke, a gas, an aerosol, or the like, or anair mixture thereof.

Each cell culture chamber is suspended in the medium chamber and issuitably held in position by a cell culture chamber support.Advantageously the cell culture chambers have a fluid passage gap in theside wall thereof. Suitably if a submersion feeding regime is to be usedthe cell culture chambers may be suitably adapted in order to ensuremedium exchange occurs at each of the cell culture chambers. Suitablythe cell culture chambers may, for example, comprise a medium passagegap(s). It is much preference that the medium passage gap(s) (ifpresent) are located in a side wall of the cell culture chambers. Cellculture chambers suitable for use in the present invention will be wellknown to those skilled in the art.

The cell culture chamber support may advantageously be comprised of asheet of material having a plurality of receiving holes therein intowhich the cell culture chambers may be lowered. The cell culture chambersupport may further act as a partial partition between the fluidexposure chamber and the medium chamber thereby ensuring that the fluidflows through the cell culture chambers before exiting the exposuredevice through the fluid outlet means.

Preferably the cell culture chamber support is formed from the samematerial as the exposure device. Preferably the material from which theexposure device and the cell culture chamber support are formed is aninert material. When referred to herein, inert material shall be takenas meaning a material that does not chemically interact with a fluidcapable of use in the aforesaid device. Suitably the exposure device andthe cell culture chamber support may be formed from a material selectedfrom the group comprising PTFE, Stainless Steel, Perspex™ and Glass.Other suitable materials will be known to those skilled in the art.

The present invention further provides a method of supplying nutrientmedium to cell culture chambers whereby nutrient supply means, mediumdirecting means and cell culture chambers are mutually arranged toprovide substantially contemporaneous nutrient medium replenishment ateach of said cell culture chambers.

The present invention further provides an exposure device for livingcell cultures having a medium chamber common to a plurality of cellculture chambers and medium directing means, the cell culture chambersand medium directing means being mutually arranged so as to providesubstantially contemporaneous medium exchange at the cell culturechambers.

In order that the invention may be easily understood and readily carriedinto effect, reference will now be made, by way of example, to thefollowing diagrammatic drawings in which:

FIG. 1 shows in longitudinal cross-section an exposure device inaccordance with the present invention, and

FIG. 2 shows in plan view an exposure device in accordance with oneembodiment of the present invention, the top portion of the device, thecell culture chambers and the medium outlet means having been removed.

FIG. 1 of the diagrammatic drawings hereof shows an exposure device 1 inaccordance with the present invention. The exposure device comprises acircular base portion 2 and a circular top portion 3 fitted together bymeans of closure screws (not shown). The top portion 3 and the baseportion 2 when closed together form a sealed unit. A rubber seal (notshown) situated between the top portion 3 and the base portion 2 ensuresno fluid leakage from the exposure device 1 during the operationthereof. Medium chamber 4 consists of a hollow well for holding nutrientmedium and is located in base portion 2 of the exposure device 1.Between the top portion 3 and the base portion 2 is located a cellculture chamber support 5. Cell culture chambers 6 are placed intoreceiving holes 21 in the cell culture chamber support 5. The base 7 ofeach cell culture chamber 6 is comprised of a permeable membrane ontowhich cell cultures 8 may be seeded and grown. Each cell culture chamber6 may further comprise an insert of inert material (not shown). Theinsert is preferably a ring of inert material, which ring is placed ontothe permeable membrane of the cell culture chamber 6. Cell cultures 8may be seeded and grown on the permeable membrane with the insert inplace. The insert is removed from the cell culture chamber before thecell cultures chambers 6 are placed into the receiving holes 21 in thecell culture chamber support 5. The insert (not shown) prevents growthof cell cultures 8 around the perimeter of the permeable membrane ofcell culture chambers 6.

Fluid passage gaps 9 are provided in each cell culture chamber 6 toallow fluid to escape from the cell culture chambers 6. The base 7 ofeach of the cell culture chambers 6 is spaced apart from the bottom ofthe exposure device to allow the medium to flow freely under each of thecell culture chambers 6 within the medium chamber 4. Medium directingmeans 10 is located, in plan view, centrally and equidistant to each ofthe cell culture chambers 6.

Medium inlet means 11 is located in the base portion 2 and providesmedium to the medium chamber 4 by means of a pump (not shown). Mediumoutlet means 12 may be a pipe attached to a second pump (not shown) forextraction of the nutrient medium from the medium chamber 4. Mediumoutlet means 12 is removable from the top portion 3 of the exposuredevice 1. The intake end of medium outlet means 12 passes through a hole22 in cell culture chamber support 5 into the medium chamber 4. Mediumoutlet means 12 may be fixed into position by a locking means (notshown). The locking means may be provided by a threaded screw having acentral bore therethrough. In this instance, medium outlet means 12 maypass through the central bore of the threaded screw.

Fluid inlet means 13 is centrally located in top portion 3 and comprisesan inlet bore 14 through an outer sleeve 15, the inlet bore 14dispersing fluid through three further radially arranged bores 16 abovefluid dispersing means 17 into fluid exposure chamber 18. Fluid outletmeans 19 is located in base side wall 20. The fluid outlet means 19 mayalternatively be attached to pump means (not shown) for rapid removal ofthe fluid.

In operation, nutrient medium (not shown) is pumped into the mediumchamber 4 (pump not shown), the nutrient medium being pre-heated to therequired temperature for cell maintenance. The nutrient medium is pumpedinto the medium chamber 4 at a fixed pumping rate until it eithercontacts the base of the cell culture chamber 7 as is required for basalfeeding of the cell cultures 8, or the medium is allowed to reach alevel in the medium chamber 4 at which the cell cultures 8 are submersedin the nutrient medium as is required for submersion feeding of the cellcultures 8.

A pump rate of the medium outlet pump is greater than the pump rate ofthe medium inlet pump rate, thus ensuring a constant level of nutrientmedium in the medium chamber 4. When the nutrient medium contacts thebottom of the medium outlet pipe 12, medium is sucked away by the actionof the outlet pump means. The respective pump rates and height of themedium outlet means should be selected to ensure the nutrient mediumlevel deviates by no more than 0.5 mm during operation of the pumps.Once the medium meniscus formed at the intake end of the medium outletpipe 12 breaks the liquid suction from the outlet pump ceases. Themedium level is thereby maintained such that medium always contacts thebase 7 of the cell culture chamber 6 during basal feeding or,alternatively always submerges the cell culture 8 to the same depthduring submersion feeding thereof. In an alternative arrangement theexposure device 1 is provided with two medium outlet means 12. Theintake end of a first medium outlet means 12 is the same distance abovethe base of the exposure device 1 as the cell cultures 8 and the intakeend of a second medium outlet means 12 is a greater distance above thebase of the exposure device 1 than the base of the cell cultures 8.Operation of the first medium outlet means 12 allows for basal feedingof the cell cultures 8, and operation of the second medium outlet means12 allows for submersion feeding of the cell cultures 8.

In a further alternative arrangement (not shown) of medium outlet means12, there is provided an inverted Y-shaped tube and switching means. Thetwo intake ends of the medium outlet means 12 may be fixed at differentdistances above the base of the exposure device 1, thus allowingswitching between basal and submersion feeding conditions. The switchingmeans may further be provided with timing means to allow switchingbetween basal and submersion feeding conditions at timed intervals.

The nutrient medium is free to flow within the medium chamber 4 suchthat it flows under the base 7 of each cell culture chamber 6. Themedium directing means 10 ensures medium exchange occurs under each cellculture chamber 6 substantially contemporaneously.

In operation, a fluid is piped through the fluid inlet means 13, and isdispersed by the fluid dispersing means 17 and into the fluid exposurechamber 18. The fluid is free to flow over the cell cultures 8. Thefluid then disperses out of the cell culture chambers 6 through fluidpassage gaps 9 and exits the exposure device 1 through fluid outletmeans 19.

In an alternative embodiment of the present invention the fluid outletmeans may be located in the top portion of the exposure device. Fluidmay disperse throughout the fluid exposure chamber 18 and out throughthe fluid outlet means 19 having dispersed into the cell culturechambers 6. In this alternative embodiment the cell culture chambers 6may have solid walls with no fluid passage gaps 9 therein.

The temperature of the nutrient medium may be maintained by placing theexposure device 1 on heating means (not shown). The heating means maysuitably be a warming-plate covered with a material capable of heattransfer to prevent hot spots on the base portion 2 of the exposuredevice 1. The material capable of heat transfer maybe bubble wrap, forexample.

In an alternative arrangement (not shown), the temperature of thenutrient medium and the exposure device 1 may be maintained by placingthe apparatus inside one or more incubators (not shown). In thisarrangement the nutrient medium and the inlet pump means may be locatedwithin a first incubator, and at least one exposure device 1 of thepresent invention may be located within a second incubator. The outletpump means may be located outwith the second incubator. The first andsecond incubators may be modified such that the apparatus within thefirst incubator are operably linked to the apparatus within the secondincubator. Furthermore the second incubator may be modified such thatthe apparatus contained therein are operably linked to the outlet pumpmeans of the present invention. The first and second incubators may bemaintained at a temperature suitable for maintenance and growth of thecell cultures 8.

In an alternative embodiment of the present invention, the externalperimeter of the exposure device 1 may be of any shape, for examplesquare or rectangular, and the medium directing means is centrallylocated within the medium chamber and is equidistant to each of the cellculture chambers.

EXAMPLE 1

The exposure device of the present invention may be used in accordancewith the following method.

At least two hours before beginning the experiment two large bottles ofnutrient medium are pre-warned to a temperature required for cellmaintenance and the apparatus are sterilised.

Costar Transwells™ with cultured cells attached to the lower membranethereof are lowered into the receiving holes in the cell chamber supportof the exposure device. The top portion of the exposure device is fittedtogether with the base portion and closed using the closure screws. Theheight of the medium outlet pipe above the base of the exposure deviceis set to facilitate basal and/or submersion feeding conditions and themedium outlet pipe is locked into position using a threaded screw. Themedium inlet and outlet pumps are attached and the fluid inlet pipe isattached to a smoking machine.

The exposure device and the medium inlet piping is then wrapped inbubble wrap to ensure full insulation. The device is placed onto awarming-plate set at the required temperature.

The medium outlet pump rate is selected such that it is greater than themedium inlet pump rate and nutrient medium is pumped into the mediumchamber of the exposure device to the level determined by the height ofthe intake end of the medium outlet pipe above the base of the exposuredevice.

The smoking machine is turned on and the smoke generated from themachine is piped into the fluid exposure chamber, via the fluid inletpipe, for a set time.

1. An exposure device for living cell cultures comprising a baseportion, a top portion, fluid inlet, fluid outlet, medium inlet, mediumoutlet, a medium chamber and a plurality of cell culture chambers,wherein the medium chamber is common to all of the cell culturechambers.
 2. An exposure device according to claim 1, wherein saidmedium chamber has medium directing means.
 3. An exposure deviceaccording to claim 2, wherein said medium directing means is formed froma raised area of said base portion of said exposure device.
 4. Anexposure device according to claim 2, wherein said medium directingmeans is an island within said medium chamber around which a nutrientmedium may flow.
 5. An exposure device according to claim 2, whereinsaid medium directing means is centrally located within said mediumchamber.
 6. An exposure device according to claim 2, wherein said mediumdirecting means is located equidistant to each of said cell culturechambers.
 7. An exposure device according to claim 1, wherein saidexposure device comprises three cell culture chambers.
 8. An exposuredevice according to claim 1, wherein the base of each of said cellculture chambers is spaced apart from the base of said exposure deviceby a gap such that, in operation, nutrient medium flows freely undereach of said cell culture chambers within said medium chamber.
 9. Anexposure device according to claim 8, wherein said gap is at least 1 mm.10. An exposure device according to claim 8, wherein said gap is about 2mm or more.
 11. An exposure device according to claim 1, wherein saidmedium inlet is located in said base portion of said exposure devicesuch that, in operation, medium flows directly into said medium chamber.12. An exposure device according to claim 11, wherein said medium inletis located in a side wall of said base portion of said exposure device.13. An exposure device according to claim 11, wherein said medium inletis located in a bottom wall of said base portion of said exposuredevice.
 14. An exposure device according to claim 1, wherein said mediuminlet is a pipe or a tube.
 15. An exposure device according to claim 1,wherein said medium outlet is spaced apart from said medium inlet. 16.An exposure device according to claim 2, wherein said medium outlet isspaced apart from said medium inlet by all of said cell culture chambersand/or said medium directing means.
 17. An exposure device according toclaim 1, wherein said medium outlet is operable to remove nutrientmedium from the top surface thereof.
 18. An exposure device according toclaim 17, wherein said medium outlet extends from the top portion ofsaid exposure device into said medium chamber.
 19. An exposure deviceaccording to claim 1, wherein said medium outlet comprises two outlets.20. An exposure device according to claim 19, wherein one of said twooutlets is positioned to allow for basal feeding of said cell cultures,and the other of said outlets is positioned to allow for submersionfeeding of said cell cultures.
 21. An exposure device according to claim1, wherein said medium outlet is a pipe or a tube.
 22. An exposuredevice according to claim 21, wherein said medium outlet is locked intosaid exposure device by a locking mechanism.
 23. An exposure deviceaccording to claim 22, wherein said locking mechanism is a threadedscrew arrangement having a central bore.
 24. An exposure deviceaccording to claim 22, wherein said locking mechanism is a frictionallock operable to adjust the position of said medium outlet tube.
 25. Anexposure device according to claim 1, wherein said medium outlet isoperably attached to a first pump and said medium inlet is operablyattached to second pump.
 26. An exposure device according to claim 25,wherein, in operation, said first pump has a controllable first pumprate and said second pump has a controllable second pump rate and saidfirst pump rate is at least equal to said second pump rate.
 27. Anexposure device according to claim 26, wherein said first pump rate isgreater than said second pump rate.
 28. An exposure device according toclaim 1, wherein said exposure device further comprises a fluid exposurechamber.
 29. An exposure device according to claim 28, wherein saidfluid exposure chamber is common to said cell culture chambers.
 30. Anexposure device according to claim 28, wherein said exposure devicefurther comprises fluid dispersing means.
 31. An exposure deviceaccording to claim 30, wherein said fluid dispersing means is operableto provide substantially contemporaneous fluid exposure to each of saidcell culture chambers.
 32. An exposure device according to claim 30,wherein said fluid dispersing means is a disc-shaped plate above saidcell culture chambers.
 33. An exposure device according to claim 1,wherein said fluid inlet means is located in said top portion of saidexposure device.
 34. An exposure device according to claim 1, whereinsaid fluid inlet is operably connected with fluid generating meanswhereby fluid is delivered to said exposure device through said fluidinlet.
 35. An exposure device according to claim 1, wherein saidexposure device further comprises a cell culture chamber support.
 36. Anexposure device according to claim 1, wherein said exposure device isformed from a material selected from the group comprising PTFE,Stainless Steel, Perspex™ and Glass.
 37. A method of supplying nutrientmedium to cell culture chambers whereby nutrient supply means, mediumdirecting means and cell culture chambers are mutually arranged toprovide substantially contemporaneous nutrient medium replenishment ateach of said cell culture chambers.
 38. An exposure device for livingcell cultures having a medium chamber common to a plurality of cellculture chambers and medium directing means, said cell culture chambersand medium directing means being mutually arranged so as to providesubstantially contemporaneous medium exchange at said cell culturechambers.
 39. (canceled)
 40. An exposure device for living cellcultures, comprising: a base portion, a top portion, a fluid inlet, afluid outlet, a medium inlet, a medium outlet, a medium chamber and aplurality of cell culture chambers, wherein the medium chamber is commonto all of the cell culture chambers, said medium chamber has a raisedarea of said base portion of said exposure device.
 42. The exposuredevice according to claim 40, wherein said raised area of said baseportion is located equidistant to each of said cell culture chambers.43. An exposure device for living cell cultures, comprising: a baseportion, a top portion, a fluid inlet, a fluid outlet, a medium inlet, amedium outlet, a medium chamber and a plurality of cell culturechambers, wherein the medium chamber is common to all of the cellculture chambers, said medium chamber has a raised area of said baseportion of said exposure device, said medium outlet locked into saidexposure device by a locking mechanism.